Paper Title
Cost- Benefit Analysis Of Two Dissimilar Warm Standby Space Shuttle System Subject To Failure Due To Damage Of The Thermal Protection System Of The Shuttle’s Wing And Failure Due To Atmospheric Hot Gas With Switch Failure
Abstract
The Space Shuttle Columbia disaster occurred on February 1, 2003, when Columbia disintegrated over Texas and
Louisiana as it reentered Earth's atmosphere, killing all seven crew members. During the launch of STS-107, Columbia's
28th mission, a piece of foam insulation broke off from the Space Shuttle external tank and struck the left wing. Most
previous shuttle launches had seen minor damage from foam shedding, but some engineers suspected that the damage
to Columbia was more serious. NASA managers limited the investigation, reasoning that the crew could not have fixed the
problem if it had been confirmed. When the Shuttle reentered the atmosphere of Earth, the damage allowed hot atmospheric
gases to penetrate and destroy the internal wing structure, which caused the spacecraft to become unstable and slowly break
apart. After the disaster, Space Shuttle flight operations were suspended for more than two years, similar to the aftermath of
the Challenger disaster. Construction of the International Space Station (ISS) was put on hold; the station relied entirely on
the Russian Federal Space Agency for resupply for 29 months until Shuttle flights resumed with STS-114 and 41 months for
crew rotation until STS-121.Several technical and organizational changes were made, including adding a thorough on-orbit
inspection to determine how well the shuttle's thermal protection system had endured the ascent, and keeping a designated
rescue mission ready in case irreparable damage was found. Except for one final mission to repair the Hubble Space
Telescope, subsequent missions were flown only to the ISS so that the crew could use it as a "safe haven". Two-unit standby
system subject to environmental conditions such as shocks, change of weather conditions etc. have been discussed in
reliability literature by several authors due to significant importance in defenses , industry etc. In the present paper we have
taken two-non-identical warm standby system with failure time distribution as exponential and repair time distribution as
general. We are considering system subject to failure due to (i) damaged thermal protection and (ii) atmospheric hot gas
requiring different types of repair facilities. Using semi Markov regenerative point technique we have calculated different
reliability characteristics such as MTSF, reliability of the system, availability analysis in steady state, busy period analysis of
the system under repair, expected number of visits by the repairman in the long run and gain-function and graphs are drawn.
Keyword- Warm Standby, Failure Due To Damaged Thermal Protection, Failure Due To Atmospheric Hot Gas, Switches
Failure.